A grounding device for use in a building such as a house or a factory is an elongate grounding bar composed of a conductive metal material and driven into vacant land in the premise. Such a grounding device and a method of constructing the grounding device are disclosed in, for example, the Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 5-182701.
The conventional method of constructing a grounding device requires the check of a site into which the grounding bar is to be driven and the nearby earth for objects buried in these places before the driving of the grounding bar. Thus, the absence of buried objects must be confirmed before the grounding device can be constructed. This disadvantageously results in the need for much time and effort for construction of the grounding device.
The grounding device composed of the grounding bar driven into the earth may fail to offer a predetermined grounding resistance owing to the large specific resistance of the earth. A plurality of grounding bars must then be driven into the earth. This disadvantageously results in the need for more time and effort for construction of the grounding device.
The grounding bar driven directly into the earth may corrode earlier owing to the moisture in the earth or the like. This may disadvantageously prevent the grounding device from providing its original functions.
In the recent years, instead of 100 VAC, 200 VAC has often been used for houses in order to deal with electric appliances with large current carrying capacities. The introduction of 200-VAC indoor distribution lines into houses has required the grounding device to be more reliable. That is, the grounding device needs to offer at most a predetermined grounding resistance and to last longer, thus protecting not only the electric appliances but also users from accidents.
An object of the present invention is to solve the problems of the conventional grounding device and the conventional method of constructing the grounding device.